1. Technical Field
The present disclosure relates to systems and methods for providing energy to biological tissue and, more particularly, to a microwave ablation surgical probe having a high strength ceramic puck assembly, and methods of use and manufacture therefor.
2. Background of Related Art
In the treatment of diseases such as cancer, certain types of cancer cells have been found to denature at elevated temperatures (which are slightly lower than temperatures normally injurious to healthy cells). These types of treatments, known generally as hyperthermia therapy, typically utilize electromagnetic radiation to heat diseased cells to temperatures above 41° C., while maintaining adjacent healthy cells at lower temperatures where irreversible cell destruction will not occur. Other procedures utilizing electromagnetic radiation to heat tissue also include ablation and coagulation of the tissue. Such microwave ablation procedures are typically performed to ablate and coagulate targeted tissue to denature or kill the tissue. Many procedures and types of devices utilizing electromagnetic radiation therapy are known in the art. Such microwave therapy is typically used in the treatment of tissue and organs such as the prostate, heart, and liver.
Presently, there are several types of microwave probes in use, e.g., monopole, dipole, and helical. A monopole antenna probe consists of a single, elongated microwave conductor exposed at the end of the probe. The probe is typically surrounded by a dielectric sleeve. A dipole antenna consists of a coaxial construction having an inner conductor and an outer conductor with a dielectric junction separating a portion of the inner conductor, which may be coupled to a portion corresponding to a first dipole radiating section, and a portion of the outer conductor which may be coupled to a second dipole radiating section. The dipole radiating sections may be configured such that one radiating section is located proximally of the dielectric junction, and the other portion is located distally of the dielectric junction. In both the monopole and dipole antenna probe, microwave energy generally radiates perpendicularly from the axis of the conductor.
The typical microwave probe has a long, thin inner conductor which extends along the axis of the probe and is surrounded by a dielectric material and is further surrounded by an outer conductor around the dielectric material such that the outer conductor also extends along the axis of the probe. In another variation of the probe, which provides for effective outward radiation of energy or heating, a portion or portions of the outer conductor can be selectively removed. This type of construction is typically referred to as a “leaky waveguide” or “leaky coaxial” antenna. Another variation on the microwave probe involves having the tip formed in a uniform spiral pattern, such as a helix, to provide the necessary configuration for effective radiation. This variation can be used to direct energy in a particular direction, e.g., perpendicular to the axis, in a forward direction (i.e., towards the distal end of the antenna), or a combination thereof.
Invasive procedures have been developed in which a microwave antenna probe may be either inserted directly into a point of treatment via a normal body orifice, or inserted percutaneously. Such invasive procedures and devices potentially provide better temperature control of the tissue being treated. Because of the small difference between the temperature required for denaturing malignant cells and the temperature injurious to healthy cells, a known heating pattern and predictable temperature control is important so that heating is confined to the tissue to be treated. For instance, hyperthermia treatment at the threshold temperature of about 41.5° C. generally has little effect on most malignant growth of cells. However, at slightly elevated temperatures above the approximate range of 43° C. to 45° C., thermal damage to most types of normal cells is routinely observed.
Structurally rigid invasive probes exist, and are typically long, narrow, needle-like antenna probes which may be inserted directly into the body tissue to directly access a site of a tumor or other malignancy. Such rigid probes generally have small diameters that aid not only in ease of use but also reduce the resulting trauma to the patient. A convenience of rigid antenna probes, that are capable of direct insertion into tissue, is that such probes may also allow for alternate additional uses in different situations. However, a dielectric junction, or puck, that separates radiating sections of a rigid probe, may be subjected to bending, compression, and rotational forces during manufacture, and during use. Such forces may lead to failure of the puck, causing mechanical or electrical failure of the probe. This effect may be exacerbated by the structural properties of suitable dielectric materials, such as porcelain or other ceramic materials, which tend to be brittle.